/******************************************************************************

    Copyright (C) 2006 Alessio Stalla (alessiostalla@gmail.com)

    This file is part of PrettyProlog.

    PrettyProlog is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    PrettyProlog is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with PrettyProlog; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    See the file COPYING for further details.

 *****************************************************************************/

package prettyprolog.engine.listeners;

/** A listener for the events that occur in a Theory. */
public interface TheoryListener {

    /** Called when a Clause is added to the Theory. */
    public void clauseAsserted(TheoryEvent e);

    /** Called when a Clause is removed from the Theory. */
    public void clauseRetracted(TheoryEvent e);
    
    /** Called when a Clause is chosen by the Engine via the nextClause() method. */
    public void clauseSelected(TheoryEvent e);
}